I'd just like to confirm that on my system disabling the SyncToVblank option in compiz solved my problem. I am now able to switch users without any problems. I suspect there are two bugs in play here that give similar symptoms as mine was definitely a compiz problem.
In reply to Nick B.
I'd just like to confirm that on my system disabling the SyncToVblank option in compiz solved my problem. I am now able to switch users without any problems. I suspect there are two bugs in play here that give similar symptoms as mine was definitely a compiz problem.
Regards,
Iain